1. Field of the Invention
The present invention relates to a device and a method for ultrasonic inspection and, more specifically, to a device and a method for ultrasonic inspection wherein the device is structured to measure the profile of the object being tested and use that data to improve the results of the ultrasonic inspection device.
2. Background Information
The use of non-destructive inspection devices which utilize ultrasonic vibrations is well known. Generally, an ultrasonic transducer, typically a piezoelectric crystal which is excited by an electrical pulse, is placed on the surface of a test object. The transducer alternately sends an ultrasonic signal and receives an echo. The piezoelectric crystal converts vibrations from the echo back into an electrical signal which can be interpreted by a control device. The control device may record and/or display the interpreted signal. Where there is a variation of the internal structure of the test object, e.g. an internal crack within a metal member, the ultrasonic transducer and control device are able to provide an image showing the location and extent of the crack. The ultrasonic transducer and control device, however, suffer from limitations that affect the accuracy of the image.
For example, the ultrasonic transducer typically has a contact surface that engages the test object. The contact surface may have a cross-sectional area of about 0.50 square inches. The ultrasonic transducer contact surface should engage the test object in a generally flat manner and the test object should engage substantially all of the ultrasonic transducer contact surface. In this configuration, the distance the ultrasonic waves and echo travel can be determined and the control device may produce a substantially accurate representation of the test object's internal structure. However, where the test object surface is uneven, the signal/response time is affected and the control device may produce an inaccurate representation of the test object's internal structure. That is, as shown in FIG. 1, an ultrasonic transducer 1 with a contact surface 2 is disposed on the flat surface of a test object 3. The test object 3 has a defect 4 extending to a depth. The ultrasonic transducer 1 sends a signal and receives a response, represented by the arrow. It is noted that the signal may be directed at an angle relative to the contact surface 2. The response is created when the signal encounters the tip 5 of the defect 4. As the ultrasonic transducer 1 is moved toward the defect 4 additional responses are collected from the signal reflecting from other parts of the defect 4. The control device interprets this data as is known in the art and creates a representation of the defect 4 including the depth at the defect lower end 5. In this example, because the test object 3 surface 8 is flat, the actual depth and the apparent depth are the same.
However, as shown in FIG. 2, where the test object 3 surface is not flat, the actual depth and the apparent depth are the not the same. That is, as shown, the defect 4 is located in a depression 6. As shown, there is a gradual transition between the normal surface of the test object 3 and the depression 6. Thus, when the ultrasonic transducer 1 is disposed above the depression 6, the signal and echo will travel the distance from the normal test object 3 surface 8, as opposed to the depression 6 surface. Thus, the control device interprets this data as if the depression 6 did not exist and, as shown, the control device will show an apparent depth that is not the actual depth of the defect 4. As shown in FIG. 3, a similar error can occur when the ultrasonic transducer 1 is disposed on the transition part of the depression 6. In this instance, the angle of the ultrasonic transducer 1 on the transition portion creates a slanted path for the signal and echo which, in turn, creates an inaccurate reading. Further, as shown in FIG. 4, if the ultrasonic transducer 1 is disposed in the depression 6 and the defect 4 is located outside of the depression 6, the signal and echo travel a shorter distance than the actual depth of the defect 4. Again, the apparent depth of the defect 4 will be inaccurate.
As shown in FIGS. 5A and 5B, another type of error may occur as the ultrasonic transducer 1 is moved over an angle in the surface of the test object 3. That is, as noted above, the ultrasonic transducer 1 detects different parts of the defect 4 as the ultrasonic transducer 1 is moved. Thus, where a defect 4 does not extend to the surface, there may be an error as to where the defect 4 begins as well as where the defect 4 ends. That is, as shown in FIG. 5, the ultrasonic transducer 1 is disposed on the transition part of the depression 6. This creates an error, as noted above, in locating the depth of the lower end 5 of the defect 4. As the ultrasonic transducer 1 is moved toward the defect 4 as shown by ultrasonic transducer 1′, and the ultrasonic transducer 1′ is located over the vertex between the transition portion of the depression 6 and the bottom of the depression 6, the ultrasonic transducer contact surface 2′ is spaced from the surface of the test object 3. Thus, for the reasons noted above, there is also an error in detecting the top end 7 of the defect 4. Thus as shown in FIG. 5B, the apparent depth of the defect 4 is not the same as the actual depth of the defect 4.
There is, therefore, a need for a device, and a method of using the device, to correct ultrasonic data based on variations in the profile of the test object 3.
There is a further need for a device, and a method of using the device, that measures the profile of a test object 3 during the ultrasonic examination.